The present invention relates to a method for forming a metal interconnection for connecting metal layers which are formed on different layers from each other in fabricating a semiconductor device.
A prior method for forming metal interconnection will be described with reference to FIG. 1 as follows.
Referring to FIG. 1, there is a sectional view of a semiconductor device after a metal interconnection is formed.
First, a field oxide 2 is formed on a substrate 1 and over the whole surface of the substrate a BPSG (Boro Phospho Silicate Glass) film 3 is formed. A first metal layer 4 having a predetermined pattern is formed on the BPSG film 3 and a first insulating layer 5 and a second insulating layer 6 are successively deposited on the BPSG film 3 including the first metal layer 4. The predetermined portions of the first insulating layer 5 and the second insulating layer 6 are selectively etched to form a via hole. A second metal layer 7 is deposited on the second insulating layer 6 to fill said via hole and is subsequently etched, thereby forming a metal interconnection.
However, the prior method has a problem that when the insulating layers are etched, the surface of the first metal layer, which is formed over a field oxide and has a relatively higher step, is damaged by plasma etching so that a natural oxide film is thickly formed.